Investigating the abundance of and information regarding exotic insects on native plants in New Zealand

Abstract

Exotic insects have ecological, economic, and human health impacts worldwide. In New Zealand, exotic insects have predominantly been prioritised based on economic impacts with less emphasis on ecological impacts. However, there is an ongoing need to understand potential future invading insects while also managing those that are already here. This research aims to increase understanding of the potential impacts of exotic insects on native New Zealand plants and to determine the usefulness of different record types for gathering data on exotic insects. Firstly, I sampled insects from select species of native plants at 18 Regional Parks around Auckland. I recorded environmental and disturbance variables and identified the insects collected to the lowest taxonomic level possible. Secondly, I downloaded over 86,000 records of exotic insect species in New Zealand from the Global Biodiversity Information Facility and analysed two record types: citizen science observation records (from iNaturalist) and specimen records (from digitised museum collections). I compared the differences between the two record types over taxonomic levels, temporal and geographic scales, and species body size. In the field study there was a significant increase in exotic insect abundance with increasing weed coverage; and some differences between plant species, with māhoe (Melicytus ramiflorus) having the highest total abundance and diversity of insects on average. The composition of insects was dominated by the exotic passionvine hopper (Scolypopa australis). In comparing record types, I found some differences between citizen science and specimen records, including the year of the record, the insect order, and the average body size of the species. Records from citizen scientists are focused on a smaller subset of exotic species, which is biased towards collecting larger bodied species and may indicate a lack of awareness of many other exotic species present in New Zealand. This research adds to the understanding of associations between native plants and exotic insects in New Zealand, and the potential impacts of these insects in native ecosystems. Additionally, this research provides insight into potential uses and biases of citizen science observation records and specimen records, specifically for exotic insects in New Zealand.